DESCRIPTION (Directly incorporated from the application) The Biostatistics Center of The George Washington University proposes to work in cooperative agreement with the National Institutes of Diabetes and Digestive and Kidney Diseases (NIDDK) to serve as the Data Coordinating Center (DCC) for a proposed multi-center clinical trial of the primary prevention of non-insulin dependent diabetes mellitus (NIDDM). Adiposity and inactivity have been established as critical factors in the etiology of glucose intolerance and are strongly associated with increased risk of glucose intolerance. We propose to determine the safety and efficacy of an intensive lifestyle intervention or prophylactic use of an oral hypoglycemic agent on the incidence of NIDDM among high risk patients (obese, minority, family history of NIDDM, history of gestational diabetes mellitus) in a state of impaired glucose tolerance (IGT). The objective of the one year planning phase is to develop a protocol, operations manual and data collection forms to be implemented in a five year full-scale clinical trial. The trial will require large-scale screening and randomization of 4,000 high risk patients with a diagnosis of IGT over a one year period in 20 clinical centers. Eligible patients will be randomized to "conventional" dietary counseling or one of the comparison groups (intensive lifestyle intervention or an oral hypoglycemic agent). Randomized patients will be followed for a minimum of four years with quarterly follow-up visits. Conversion from a state of IGT to overt NIDDM will be determined by semi-annual 2-hour oral glucose tolerance tests (OGTTs) following a 75 g glucose load confirmed by a central laboratory. Covariates and secondary outcomes include carotid ultrasound imaging, electrocardiograms, serum lipids, albumin excretion rate, adiposity, insulin sensitivity, hemoglobin A1c, and fundus photographs. The specific aims of the DCC are to provide centralized support and biostatistical consultation in the development of the patient management protocols, operations manual, data collection forms and randomization procedures; implementation of a data processing system including data quality assessment; interim analysis of protocol performance, patient safety and treatment efficacy; and final analysis for publication of the results in collaboration with the clinical investigators.